<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			div{
				border: 1px solid red;
			}
			.p{
				position: relative;
				width: 500px;
				height: 500px;
				
			}
			.s{
				width: 200px;
				height: 200px;
				position: absolute;
				top: 0;
				left: 0;
				bottom: 0;
				right: 0;
				margin: auto;
			}
		</style>
	</head>
	<body>
		<div class="p">
			<div class="s"></div>
		</div>
	</body>
</html>
